The present invention relates to a spacer for a plurality of fuel rods, arranged vertically in a nuclear reactor, comprising a plurality of mutually equal cells which are each intended for one fuel rod, each cell only having one vertical symmetry plane and comprising an upper and a lower polygon ring, which are interconnected by means of at least one oblong spring, each polygon ring containing a plurality of polygon sides formed from vertical sheet metal portions, among them four connecting sides which are parallel in pairs and which are each welded to a connecting side in a corresponding adjacent cell, said spring being constructed with a middle portion lying in a vertical plane with a contact projection directed towards the vertical axis of the cell.
A spacer of this general type is suggested in British Pat. No.1,480,649.
In a nuclear reactor it is inevitable that certain fuel rods in a fuel bundle give a higher thermal power than the remaining fuel rods. It is known to provide a spacer with deflection screens in order to supply cooling water flowing along a fuel rod with a horizontal speed component, so that the cooling water from fuel rods a with relatively high power can be mixed with cooling water from fuel rods with lower power already in the vicinity of the lower end of the fuel bundle. However, such deflection screens have the disadvantage that, if used to a large extent, they result in a considerable increase in the coefficient of pressure fall of the spacer. In addition, deflection screens increase the amount of neutron-absorbing material.